1. Field of the Invention
This invention is directed to the discovery that sulfurized phenols, i.e., phenol sulfides, disulfides, polysulfides and oligomers thereof as well as mixtures of the foregoing prepared for example by reaction phenol with sulfur halides are oxidation inhibitors, antiwear and extreme pressure additives for organic compositions such as oils of lubricating viscosity, solid lubricants such as greases prepared from said oils and functional fluids such as hydraulic fluids. This invention is more particularly directed to a method of improving the anti-corrosion properties of lubricant compositions containing said sulfurized phenols comprising treating said sulfurized phenols with alkyl vinyl ethers thereby making them far less corrosive or even non-corrosive to metals, particularly to copper or copper-containing alloys.
2. Description of the Prior Art
Phenol sulfides, phenols disulfides, polysulfides, and mixtures thereof as well as oligomers thereof are commonly known as "sulfurized phenols" have been previously described in the prior art as oxidation inhibitors, antiwear additives and load carrying additives for lubricants. These sulfurized phenols or phenol sulfides were generally found to be corrosive to metals such as copper and copper alloys which are widely used as bearings and bearing liners. In order to make use of the aforementioned phenol sulfides and sulfurized phenols in lubricants co-additives have been required to protect against such metal corrosion. These co-additives have included metal passivators such as benzotriazole, toluotriazole, and other substituted triazoles, and copper corrosion inhibitors such as bis-tertiary-alkyl disulfide derivatives of 1,3,4-thiadiazoles and 1,2,5-thiadiazoles as well as derivatives of 2-mercaptobenzothiazole. The use of such co-additives is expensive and the source of further complications in lubricant formulations. For example, such use may require solubilizers, or the use of such co-additives may require an additional step in blending the lubricant formulations.
The copper strip test is frequently and widely used to determine the corrosive properties of lubricants and lubricant additives and has been a major disqualifier of phenol sulfide additives. Elemental sulfur present in the product mix, either dissolved or loosely bound, may be responsible for poor copper strip ratings. Corrosive sulfur may also be produced by (e.g., thermal or catalyzed) extrusion from phenol di- and polysulfides. Several methods to resolve the corrosion problem have been explored. However, the present invention directed specifically to a method of controlling or inhibiting the corrosion of copper or copper containing metals (e.g., brass) has not been previously disclosed by any prior art references known to applicant.